KR100809233B1 - An apparatus for automatically controlling exposure of image sensor - Google Patents

Abstract

An automatic exposure control apparatus of an image sensor module of the present invention is an automatic exposure control apparatus applied to an image sensor module including a lens unit, an image sensor unit including a shutter, and an image signal processing unit. A luminance calculator for extracting an average luminance from the image signal of the; A luminance correction determining unit that determines the speed fixing or correction of the exposure adjustment shutter based on the luminance error value between the average luminance from the luminance calculating unit and a predetermined reference luminance; A correction path controller for controlling direct correction when the luminance error value is included in a predetermined small error range when determining the speed correction, and controlling filtering correction when it is out of the small error range; A digital filter for filtering the luminance error value and outputting a luminance error filtering value according to the control of the correction path controller; A shutter speed correction unit correcting a current shutter speed value using a luminance error value from the speed correction controller or a luminance error filtering value from the digital filter unit to provide a controlled shutter speed value; And a shutter speed control unit controlling a speed of a shutter included in the image sensor unit by using the control shutter speed value.

Image sensor module, automatic, exposure control

Description

Automatic exposure control device and method of image sensor {AN APPARATUS FOR AUTOMATICALLY CONTROLLING EXPOSURE OF IMAGE SENSOR}

1 is a block diagram of an image sensor of a conventional digital camera.

2 is a block diagram of an automatic exposure apparatus of an image sensor according to the present invention;

3 is a block diagram of a digital filter of the present invention.

Figure 4 is a graph of the response characteristics of the digital filter of the present invention.

5 is a response characteristic graph showing an output waveform to the step waveform input of the digital filter of the present invention.

Figure 6 is an average luminance-shutter speed correlation graph for explaining the operation of the automatic exposure control apparatus according to the present invention.

7 is a graph illustrating a method of calculating luminance characteristics for each shutter speed according to the present invention.

8 is a flowchart showing a method for automatically controlling exposure of an image sensor according to the present invention.

9 is a flowchart showing a filtering process according to the present invention.

Explanation of symbols on the main parts of the drawings

100 lens unit 200 image sensor unit

300: image signal processor 410: luminance calculator

420: luminance correction determination unit 430: correction path control unit

440: digital filter unit 441: multiplier

442: integer conversion unit 443: first register

444: second register 445: coefficient selector

450: shutter speed correction unit 460: shutter speed control unit

Sc: Current Shutter Speed Sn: Control Shutter Speed Value

ISc: current shutter speed index value ISn: control shutter speed index value

Yavr: average luminance Yref: reference luminance

IYavr: average luminance index value IYref: reference luminance index value

Err-index: Luminance error index value Err-filtering: Luminance error filtering value

MER: Micro Error Range

The present invention relates to an apparatus and method for automatically controlling exposure of an image sensor applied to a camera module. In particular, by controlling an appropriate exposure using an average luminance without using a microcontroller and changing a shutter speed using a digital filter, The present invention relates to an automatic exposure control apparatus and method for an image sensor that is active and operates at high speed in response to a sudden brightness change or a frequent brightness change of an image.

In general, a general camera performs an automatic exposure control for automatically and appropriately adjusting the brightness of an input image. The automatic exposure control is performed through the aperture ratio of the aperture and the shutter speed.

On the other hand, in a digital camera, a solid-state image sensor such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) is used as an image sensor, and in such a digital camera, the amount of exposure is adjusted by adjusting the time taken by the image sensor. Adjust In this case, the time captured by the image sensor corresponds to the speed of the electronic shutter, and the brightness of the image is adjusted by changing the speed of the electronic shutter.

1 is a block diagram of an image sensor of a conventional digital camera.

The image sensor of the conventional digital camera shown in FIG. 1 includes a lens unit 10 that receives an image and a shutter, and captures an image from the lens unit 10 through the shutter to generate an electrical image signal. The image sensor unit 20 for converting, the image signal processor 30 for restoring the image signal through the image sensor unit 20 to the image, and calculates the brightness in the image signal from the image signal processor 30 And a microcontroller 40 for controlling the shutter of the image sensor 20 according to the difference between the calculated brightness and the reference brightness.

The exposure control process in the microcontroller 40 will be described below.

The micro-controller calculates the brightness of each frame of the current image (S41), calculates a difference between the calculated brightness and the reference brightness (S42), and calculates a brightness compensation value according to the difference of the brightness. After calculating (S43), the compensation value is added to the current exposure conversion value to obtain a future application value (S44), and the approximated multiple value is obtained by approximating the future application value by a multiple of the minimum exposure time (S45), The shutter of the image sensor 20 is controlled using the drain value (S46).

However, in the exposure control method of the conventional digital camera, when the exposure change of the input image suddenly changes while performing an operation for finding an appropriate exposure using a dedicated micro-controller, the appropriate exposure is found. There is a problem that takes a long time.

Further, in the process of calculating based on the information on the brightness of the image signal, the data on the brightness is too large, there is a problem that the calculation takes a long time.

In addition, when the exposure changes abruptly frequently for a short time, the microcontroller cannot recognize a sudden change in exposure, and thus, when there is a sudden change in exposure, there is a problem in that it cannot be controlled at an appropriate brightness.

SUMMARY OF THE INVENTION The present invention has been proposed to solve the above problems, and its object is not to use a microcontroller, but to control the appropriate exposure by using the average brightness, and to change the shutter speed using a digital filter, thereby causing a sudden An object of the present invention is to provide an apparatus and method for automatically controlling exposure of an image sensor that is active and high speed in response to a luminance change or a frequent luminance change.

In order to achieve the above object of the present invention, the automatic exposure control apparatus of the image sensor module of the present invention includes a lens unit for receiving an image and a shutter, and the image is taken from the lens unit through the shutter An automatic exposure control apparatus applied to an image sensor module including an image sensor unit for converting an electrical image signal and an image signal processor for restoring an image signal through the image sensor unit into an image, the image from the image signal processor A luminance calculator for extracting an average luminance from the signal; A luminance correction determining unit determining a speed fixing or a speed correction of the exposure adjustment shutter based on a luminance error value corresponding to an error between the average luminance from the luminance calculating unit and a preset reference luminance; In determining the speed correction, if the luminance error value is within a predetermined microerror range, direct compensation of the speed of the shutter is controlled. If the luminance error value is out of a predetermined microerror range, filtering correction of the speed of the shutter is performed. A correction path control unit controlling the control; A digital filter for filtering the luminance error value and outputting a luminance error filtering value according to the control of the correction path controller; A shutter speed correction unit correcting a current shutter speed value using a luminance error value from the speed correction controller or a luminance error filtering value from the digital filter unit to provide a controlled shutter speed value; And a shutter speed control unit controlling a speed of a shutter included in the image sensor unit by using the control shutter speed value.

The luminance calculator is configured to calculate the average luminance of the image at the current shutter speed for each frame.

The luminance correction determining unit converts the average luminance into an average luminance index value by referring to a first lookup table to which the average luminance index value for each average luminance is mapped in advance, and the reference luminance index value previously assigned to a predetermined reference luminance. The luminance error index value corresponding to the error with the average luminance index value is obtained. When the luminance error index value is '0', the current shutter speed value is determined as the control shutter speed value, and the luminance error index value is '0'. Otherwise, the correction of the current shutter speed value is controlled.

When the luminance error index value is included in a preset small error range, the correction path controller controls direct correction of a current shutter speed index value corresponding to the average luminance by setting the luminance error index value. If not included in the small error range, it is characterized in that the filtering correction of the current shutter speed index value.

The digital filter unit may output the luminance error filtering value by filtering the luminance error index value under the control of the speed compensation controller.

The shutter speed correction unit may determine a controlled shutter speed index value by correcting a current shutter speed index value using a luminance error index value from the speed correction controller or a luminance error filtering value from the digital filter unit. do.

The shutter speed control unit converts the control shutter speed index value into a control shutter speed value by referring to a second lookup table to which the control shutter speed value for each control shutter speed index value is mapped in advance, and uses the control shutter speed value. And controlling the speed of the shutter of the image sensor unit.

The predetermined micro-error range is set to be greater than or equal to '-2' and less than or equal to '2'.

The digital filter may include: a multiplier for multiplying a predetermined coefficient by the luminance error index value; An integer converter configured to convert an output value from the multiplier to a nearest integer value and output an error filtering value; A first register for storing a first difference value corresponding to a difference between a luminance error index value and the error filtering value for one previous frame of the current frame of the image signal; A second register for storing a first difference value corresponding to a difference between a luminance error index value and the error filtering value for two previous frames of the current frame of the image signal; And a coefficient selector configured to select one of preset filter coefficients according to the luminance error index value, the first difference value, and the second difference value.

In addition, the automatic exposure control method of the image sensor module of the present invention includes an image sensor for receiving an image and a shutter, and an image sensor for capturing the image from the lens unit through the shutter and converting the image into an electrical image signal An automatic exposure control apparatus applied to an image sensor module including an image signal processing unit for restoring an image signal through the image sensor unit to an image, the average calculating an average luminance of an image at a current shutter speed for each frame. Luminance calculation step; An index conversion step of converting the average luminance into an average luminance index value by referring to a first lookup table to which an average luminance index value for each average luminance is mapped in advance; An error calculating step of obtaining a luminance error index value corresponding to an error between a reference luminance index value previously assigned to a preset reference luminance and the average luminance index value; A speed fixing step of determining a current shutter speed value as a control shutter speed value when the luminance error index value is '0'; When the luminance error index value is not '0', when the luminance error index value is included in a preset small error range, the current shutter speed index value is corrected using the luminance error index value to control the shutter speed index value. A direct correction step of determining; A filtering step of obtaining a luminance error filtering value by filtering the luminance error index value when the luminance error index value is not included in a predetermined small error range; A filtering correction step of determining a control shutter speed index value by correcting a current shutter speed index value by using the luminance error filtering value from the digital filter unit; A speed conversion step of converting the control shutter speed index value into a control shutter speed value by referring to a second lookup table to which the shutter speed value for each control shutter speed index value is mapped; And a controlling step of controlling the speed of the shutter of the image sensor unit by using the control shutter speed value.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings referred to in the present invention, components having substantially the same configuration and function will use the same reference numerals.

2 is a block diagram of an automatic exposure apparatus of an image sensor according to the present invention.

Referring to FIG. 2, the image sensor according to the present invention includes a lens unit 100 that receives an image and a shutter, and captures an image from the lens unit 100 through the shutter to generate an electrical image signal. The image sensor unit 200 for converting the image signal to the image sensor, the image signal processor 300 for restoring the image signal through the image sensor unit 200 to the image, and the average luminance from the image signal processor 300 It includes an automatic exposure control device 400 for controlling the shutter speed of the image sensor unit 200.

The automatic exposure control apparatus 400 may include a luminance calculator 410 extracting an average luminance from the image signal from the image signal processor 300, an average luminance from the luminance calculator 410, and a preset reference luminance. A luminance correction determining unit 420 that determines the speed fixing or the speed correction of the exposure adjustment shutter based on the luminance error value corresponding to the error of the light source, and the luminance error value is included in the predetermined minute error range when the speed correction is determined. A correction path controller 430 for controlling direct correction of the shutter speed and controlling filtering correction of the shutter speed when the luminance error value is out of a preset small error range, and the correction path controller 430. A digital filter unit 440 for filtering the luminance error value and outputting a luminance error filtering value according to control of the luminance error value, the luminance error value from the speed compensation control unit 430, The shutter speed correction unit 450 corrects the current shutter speed value using the luminance error filtering value from the digital filter unit 440 to provide a control shutter speed value, and the image is controlled using the control shutter speed value. It includes a shutter speed control unit 460 for controlling the speed of the shutter included in the sensor unit 120.

The luminance calculator 410 calculates the average luminance Yavr of the image at the current shutter speed Sc for each frame and outputs the average luminance for each frame.

The luminance correction determiner 420 converts the average luminance Yavr into an average luminance index value IYavr with reference to a first lookup table in which the average luminance index value for each average luminance is previously mapped, and then preset reference value. The luminance error index value Err-index corresponding to an error between the reference luminance index value IYref preassigned to the luminance Yref and the average luminance index value IYavr is obtained, and the luminance error index value Err- is obtained. If the index) is '0', the current shutter speed value Sc is determined as the control shutter speed value Sn. If the luminance error index value Err-index is not '0', the current shutter speed value Sc Control the calibration.

If the luminance error index value Err-index is included in a predetermined minimum error range (MER) under the control of the luminance correction determiner 420, Controls the direct correction of the current shutter speed index value ISc corresponding to the average luminance, and controls the filtering correction of the current shutter speed index value ISc when not included in the preset small error range MER.

The digital filter unit 440 filters the luminance error index value Err-index under the control of the speed correction controller 430 and outputs an luminance error filtering value Err-filtering.

The shutter speed correction unit 450 uses the luminance error index value Err-index from the speed correction control unit 430 or the luminance error filtering value Err-filtering from the digital filter unit 440. The current shutter speed index value ISc is corrected to determine the control shutter speed index value ISn.

The shutter speed control unit 460 converts the control shutter speed index value ISn into a control shutter speed value Sn by referring to a second lookup table to which the control shutter speed value for each control shutter speed index value is mapped in advance. The shutter speed of the image sensor unit 120 is controlled using the control shutter speed value Sn.

3 is a block diagram of a digital filter of the present invention.

Referring to FIG. 3, the digital filter 440 includes a multiplier 441 that multiplies a predetermined coefficient by the luminance error index value Err-index, and an output value from the multiplier 441 to a nearest integer value. An integer converter 442 for converting and outputting an error filtering value (Err-filtering), a luminance error index value (Err-index) and the error filtering value (Err) for one previous frame of the current frame of the image signal a first register 443 which stores a first difference value corresponding to a difference value with respect to -filtering), an luminance error index value (Err-index) and the error for two previous frames of the current frame of the image signal; A second register 444 for storing a first difference value corresponding to a difference value between the filtering value Err-filtering, the luminance error index value Err-index, the first difference value DV1, and a first difference value; Coefficient to select one among preset filter coefficients according to the secondary difference value (DV2) It includes a selection unit 445.

As the digital filter of the present invention, a first order Infinite Impulse Response (IRR) filter may be used.

Figure 4 is a graph of the response characteristics of the digital filter in the present invention.

4 is a graph showing the characteristics of the digital filter of the present invention responding at different coefficients, each response curve is a curve showing a slowly rising response as the curves are different in the time constant to reach a steady state Using the coefficients increases the time constant to reach a steady state, that is, it takes a long time to find the appropriate exposure. Alternatively, using a curve coefficient with a steeply rising response, the time constant to reach a steady state is small, i.e., an appropriate exposure can be found in a short time.

5 is a response characteristic graph showing an output waveform with respect to the step waveform input of the digital filter of the present invention.

In Fig. 5, when the step waveform transitioning from '0' to '1' is input to the digital filter of the present invention, the output waveform of the digital filter of the present invention is shown. At this time, in Fig. 5, the time after the point '1' is output from the output of the digital filter of the present invention is referred to as a stable state, the time from '0' to '1' is referred to as the time constant.

6 is an average luminance-shutter speed correlation graph for explaining the operation of the automatic exposure control apparatus according to the present invention.

In FIG. 6, the vertical axis of the graph represents the average luminance Yavr of the image, and the horizontal axis of the graph represents the shutter speed S. Referring to these graphs, the slower the shutter speed S, the higher the average luminance Yavr. The faster the shutter speed S, the lower the average brightness.

7 is a graph illustrating a method of calculating luminance characteristics for each shutter speed according to the present invention.

In Fig. 7, the dotted line is a luminance characteristic graph with respect to the shutter speed of the image sensor, and the luminance characteristic graph required for the automatic exposure control represented by the solid line is calculated using this dotted line characteristic.

8 is a flowchart illustrating a method for automatically controlling exposure of an image sensor according to the present invention.

In FIG. 8, S100 is an average luminance calculation step of calculating the average luminance Yavr of the image at the current shutter speed Sc for each frame. S200 is an index conversion step of converting the average luminance Yavr into an average luminance index value IYavr by referring to a first lookup table in which the average luminance index value for each average luminance is mapped in advance. S300 is an error calculating step of obtaining a luminance error index value Err-index corresponding to an error between the reference luminance index value IYref and the average luminance index value IYavr previously assigned to a predetermined reference luminance Yref. . S400 is a speed fixing step of determining the current shutter speed value Sc as the control shutter speed value Sn when the luminance error index value Err-index is '0'. In operation S500, when the luminance error index value Err-index is not '0', when the luminance error index value Err-index is included in a predetermined minimum error range (MER), the luminance error index is determined. This is a direct correction step of determining the control shutter speed index value ISsc by correcting the current shutter speed index value ISc using the index value Err-index. When the luminance error index value Err-index is not included in the predetermined small error range MER, S600 filters the luminance error index value Err-index to filter the luminance error filtering value Err-filtering. This is a filtering step. S700 is a filtering correction step of determining the control shutter speed index value ISsc by correcting the current shutter speed index value ISc by using the luminance error filtering value Err-filtering from the digital filter unit 440. S800 converts the control shutter speed index value ISn into a control shutter speed value Sn by referring to a second lookup table to which the shutter speed value Sn for each control shutter speed index value ISn is mapped. Step. S900 is a control step of controlling the speed of the shutter of the image sensor unit 120 using the control shutter speed value Sn.

9 is a flowchart showing a filtering process according to the present invention.

In FIG. 9, S610 is a first difference value corresponding to a difference value between the luminance error index value Err-index and the error filtering value Err-filtering for one previous frame of the current frame of the image signal. The first storage step is to store. S620 stores a first difference value corresponding to a difference between a luminance error index value Err-index and an error filtering value Err-filtering for two previous frames of the current frame of the image signal; Save step. S630 is a coefficient selection step of selecting a coefficient from among predetermined filter coefficients according to the luminance error index value Err-index, the first difference value DV1, and the second difference value DV2, and providing the coefficient to the multiplication step. . S640 is a multiplication step of multiplying the coefficient by the luminance error index value Err-index to output a multiplication value. S650 is an integer conversion step of outputting an error filtering value by converting the multiplication value to the nearest integer value.

Hereinafter, the operation and effects of the present invention will be described in detail with reference to the accompanying drawings.

An operation of the automatic exposure control apparatus and method of the image sensor module according to the present invention will be described with reference to FIGS. 2 to 9.

First, referring to FIG. 2, the automatic exposure control apparatus of the image sensor module of the present invention is applied to an image sensor module. Briefly referring to the operation of the image sensor module, an image is obtained through the lens unit 100 of the image sensor module. Is incident to the image sensor unit 200. At this time, the image sensor unit 200 includes a shutter and captures an image from the lens unit 100 through the shutter, converts the image into an electrical image signal, and outputs an image signal to the image signal processing unit 300. In addition, the image signal processing unit 300 restores an image signal through the image sensor unit 200 to an image.

In such an image processing process, the present invention is a technique for automatically controlling the speed of a shutter while monitoring the brightness of an image, which will be described.

Referring to FIG. 2, the luminance calculator 410 of the automatic exposure control apparatus of the present invention extracts the average luminance from the image signal from the image signal processor 300 and outputs the average luminance to the luminance correction determiner 420.

For example, the luminance calculator 410 calculates the average luminance Yavr of the image at the current shutter speed Sc for each frame and calculates the average luminance Yavr for each frame by the luminance correction determiner 420. Output to (corresponding to S100 of FIG. 8).

Next, the luminance correction determining unit 420 determines the speed fixing or the speed correction of the exposure adjustment shutter based on the luminance error value corresponding to the error between the average luminance from the luminance calculating unit 410 and a predetermined reference luminance. The shutter speed controller 460 controls the shutter speed to be fixed or corrected, and provides a luminance error value to the correction path controller 430.

For example, the luminance correction determiner 420 converts the average luminance Yavr into an average luminance index value IYavr by referring to a first lookup table in which the average luminance index value for each average luminance is previously mapped. (Corresponding to S200 of FIG. 8), a luminance error index value Err-index corresponding to an error between a reference luminance index value IYref previously assigned to a preset reference luminance Yref and the average luminance index value IYavr. ) (Corresponding to S300 of FIG. 8), and determining whether the luminance error index value (Err-index) is '0' (corresponding to S410 of FIG. 8), and the luminance error index value (Err-index). If () is '0', the current shutter speed value Sc is determined as the control shutter speed value Sn (corresponding to S420 of FIG. 8), and if the luminance error index value Err-index is not '0', The correction of the shutter speed value Sc is controlled.
Here, an example of the first lookup table may be shown in Table 1 below.
Average luminance (Yavr) Average luminance index value (IYavr) 228 10 222 9 210 8 191 7 162 6 126 5 89 4 60 3 40 2 29 One 23 0

Next, when the speed correction is determined, the correction path controller 430 controls direct correction of the shutter speed when the luminance error value is within a predetermined microerror range, and the luminance error value is a predetermined micro error. If out of the range, the digital filter unit 440 controls the filtering correction of the shutter speed.

For example, the correction path controller 430 may be configured to have a minimum error range (MER) of which the luminance error \ index value (Err-index) is preset according to the control of the luminance correction determiner 420. When included in the control, the direct correction of the current shutter speed index value (ISc) corresponding to the average brightness, and if not included in the predetermined micro-error range (MER), filtering correction of the current shutter speed index value (ISc) To control.

The predetermined small error range is a range for determining whether the luminance error is a small change, which may be set differently according to the use environment of the application system. For example, the predetermined small error range is greater than or equal to '-2', It may be set to 'less than or equal to' (corresponding to S510 of FIG. 8).

Next, the digital filter unit 440 filters the luminance error value under the control of the correction path controller 430 and outputs the luminance error filtering value to the shutter speed correction unit 450.

For example, the digital filter unit 440 filters the luminance error index value Err-index under the control of the speed correction controller 430 and outputs an luminance error filtering value Err-filtering ( Corresponds to S600 in FIG. 8).

Next, the shutter speed correction unit 450 corrects and controls the current shutter speed value by using the luminance error value from the speed correction controller 430 or the luminance error filtering value from the digital filter unit 440. The shutter speed value is provided to the shutter speed controller 460.

More specifically, the shutter speed correction unit 450 may use the luminance error index value Err-index from the speed correction control unit 430 at the time of the direct correction control of the correction path control unit 430. The shutter speed index value ISc is corrected (corresponds to S520 of FIG. 8). In contrast, the shutter speed correction unit 450 uses the luminance error filtering value (Err-filtering) from the digital filter unit 440 to control the current shutter speed during the filtering correction control of the correction path controller 430. The index value ISc is corrected (corresponds to S700 in FIG. 8). Through this correction process, the shutter speed correction unit 450 determines the control shutter speed index value ISn.

For example, the control shutter speed index value ISn can be obtained by adding the luminance error index value Err-index to the current shutter speed index value ISc, or the control shutter speed index value ISn is The luminance error filtering value Err-filtering may be added to the current shutter speed index value ISc.

Next, the shutter speed control unit 460 controls the speed of the shutter included in the image sensor unit 120 using the control shutter speed value.

For example, the shutter speed control unit 460 controls the shutter speed of the image sensor unit 120 at the previous shutter speed when the brightness correction control unit 420 controls the shutter speed. In contrast, in the shutter speed correction control of the luminance correction determiner 420, the control shutter speed index value ISn is referred to by referring to a second lookup table to which the control shutter speed value for each control shutter speed index value is mapped in advance. The shutter speed of the image sensor unit 120 is controlled using the control shutter speed value Sn by converting to a control shutter speed value Sn (corresponding to S900 of FIG. 8).
Here, an example of the second lookup table may be shown as Table 2 below.
Control Shutter Speed (sec) (Sn) Control Shutter Speed Index Value (ISc) One 0 1/2 One 1/4 2 1/8 3 1/15 4 1/30 5 1/60 6 1/125 7 1/250 8 1/500 9 1/1000 10

An operation of the digital filter 440 will be described in detail with reference to FIGS. 3 and 9.

3 and 9, when power is applied, the first register 1 443 and the second register 2 444 have an initial value '0', and then, the first of the digital filter 440. The register 443 may include a first difference value corresponding to a difference between the luminance error index value Err-index and the error filtering value Err-filtering for one previous frame of the current frame of the image signal. DV1) (corresponding to S610 of FIG. 9). The second register 444 corresponds to a difference between a luminance error index value Err-index and an error filtering value Err-filtering for two previous frames of the current frame of the image signal. The second difference value DV2 is stored (corresponding to S620 of FIG. 9).

In addition, the coefficient selector 445 of the digital filter 440 may preset filter coefficients according to the luminance error index value Err-index, the first difference value DV1, and the second difference value DV2. One of them is selected (corresponds to S630 of FIG. 9).

The multiplier 441 of the digital filter 440 multiplies a predetermined coefficient by the luminance error index value Err-index and outputs the result to the integer converter 442 (corresponding to S640 of FIG. 9). The integer converter 442 converts the output value from the multiplier 441 into the nearest integer value and outputs an error filtering value (Err-filtering) (corresponding to S650 of FIG. 9).

For example, the coefficient selector 445 will be described in detail.

The luminance error index value Err-index is defined as a value obtained by subtracting the reference luminance index value IYref from the average luminance index value IYavr, and the first difference value DV1 is one frame than the current frame. The error filtering value Err-filtering corresponding to the output of the digital filter unit 440 is subtracted from the luminance error index value Err-index corresponding to the input of the digital filter unit 440 with respect to the previous frame. The second difference value DV2 is defined as one value, and a luminance error index value Err-index corresponding to an input of the digital filter unit 440 for a frame two frames before the current frame. A case in which an error filtering value (Err-filtering) corresponding to an output of the digital filter unit 440 is defined as a value obtained by subtracting the following will be described.

If both the luminance error index value Err-index, the first difference value DV1 and the second difference value DV2 have the same sign, a large coefficient value is selected among preset coefficients, and the luminance error index value Err -index) and the first difference value is the same only if the sign of the middle coefficient of the predetermined coefficient is selected, and if the sign of the luminance error index value (Err-index) is different from the sign of the first difference value predetermined coefficient You can select a smaller coefficient value.

Through this process, the input value of the digital filter of the present invention is multiplied by the selected coefficient and then converted into an integer value and output. As soon as one image frame is finished, a difference value (input value-output value) between the input value and the output value of the digital filter is stored in the first register 443, and at the same time, the value of the first register 443 is equal to the second value. Stored in register 444. The digital filter of the present invention repeats the above operation.

In addition, the coefficient of the digital filter of the present invention can be selected and used by calculating a number of factors according to the characteristics of the image sensor to which the present invention is applied.

Referring to FIG. 4, the response curves illustrated in FIG. 4 are curves having different time constants for reaching the stable state of the digital filter unit of the present invention. Referring to FIG. 4, the use of a coefficient of a curve showing a slowly rising response increases the time constant for reaching a stable state. In other words, finding the appropriate exposure takes a long time. In addition, when the coefficient of the curve showing a steeply rising response is used, the time constant for reaching a stable state is small. As a result, an appropriate exposure is found in a short time.

For example, in the case of a sudden change in luminance, such as when lighting a light in a dark room, active shutter speed can be changed by using a digital filter having a coefficient of steep response. In addition, the coefficient values used in the digital filter are not fixed values applied to all image sensor modules and can be modified according to the characteristics of the image sensor to which the present invention is applied, thereby providing high flexibility.

On the other hand, in the automatic exposure control apparatus of the present invention, as described above, when the shutter speed needs to be largely corrected in order to correct the exposure properly, the shutter is controlled using a digital filter unit having response curves of different time constants shown in FIG. 4. Speed can be processed quickly and actively.

Referring to FIG. 5, when the step waveform transitioning from '0' to '1' is input to the digital filter of the present invention, the output waveform of the digital filter of the present invention is shown. At this time, in Fig. 5, the time after the point '1' is output from the output of the digital filter of the present invention is referred to as a stable state, the time from '0' to '1' is referred to as the time constant.

An operation description of the automatic exposure control apparatus of the present invention as described above will be described with reference to FIG. 6.

Referring to the graph of FIG. 6, the slower the shutter speed S, the higher the average luminance Yavr, and the faster the shutter speed S, the lower the average luminance. In this case, the reference luminance Yref has a center value among the luminance allocation values.

Meanwhile, Table 1 shows an example in which continuous values are assigned to the shutter speed and the average luminance according to the characteristics of the image sensor in which the automatic exposure control apparatus of the present invention is used. In Table 3 below, the value assigned to the reference luminance index IYref will be described for the case where the center value '5' is assigned.

Shutter speed (sec) (Sn) Shutter speed index value (ISc) Average luminance (Yavr) Average luminance index value (IYavr) One 0 228 10 1/2 One 222 9 1/4 2 210 8 1/8 3 191 7 1/15 4 162 6 1/30 5 126 5 1/60 6 89 4 1/125 7 60 3 1/250 8 40 2 1/500 9 29 One 1/1000 10 23 0

In Table 3, the shutter speed may be referred to as the control shutter speed and the current shutter speed, and the shutter speed index value may also be referred to as the control shutter speed index value and the current shutter speed index value.
For example, referring to Table 3, when the average luminance Yavr is "191", the average luminance index value IYavr becomes "7", and at this time, the reference luminance index value IYref. ), The luminance error \ index value (Err-index) is " 2 (7-5) ", and the control shutter speed index value ISn is the luminance error index value. (Err-index) "2" and the current shutter speed index value (ISc) "3" are added to "5", which corresponds to the shutter speed "1/30".

The shutter speed " 1/8 " corresponding to " 3 " of the current shutter speed index value ISc is corrected to the shutter speed " 1/30 ", so that the shutter speed can be controlled faster because the brightness is too bright. Will be.

As described above, according to the present invention, the exposure of the image incident on the image sensor is determined according to the shutter speed, and as the shutter speed increases, the average luminance of the input image decreases, and when the shutter speed decreases, the average of the input image Since the luminance is high, graphing it has a certain shape.

Accordingly, the average brightness is obtained from the current shutter speed, and the new shutter speed is determined by comparing with the shutter speed at the already stored reference brightness, and the new shutter speed is input to the digital filter, and the output value is gradually changed to the new shutter speed. So that a natural output image can be obtained.

Therefore, according to the present invention, the above-described control is performed on the basis of the luminance error by comparing the average luminance index value and the reference luminance index value, which show the luminance of the current image, and as a result of this control, the current average luminance tracks the reference luminance. I will go.

Referring to FIG. 7, the dotted line is a luminance characteristic graph with respect to the shutter speed of the image sensor, and the luminance characteristic graph required for the automatic exposure control represented by the solid line is calculated using this dotted line characteristic. A slope of a straight line corresponding to a section showing linear characteristics based on the reference luminance value Yref is obtained from the dotted line of FIG. 7, and corresponds to a section saturated with the maximum luminance value Ymax and the minimum luminance value Ymin. Find the slope of a straight line. In this case, a luminance characteristic graph of the shutter speed applied to the automatic exposure control represented by the solid line of FIG. 7 is calculated using the value and the luminance value assigned to the shutter speed at each inclination.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, but is defined by the claims, and the apparatus of the present invention may be substituted, modified, and modified in various ways without departing from the spirit of the present invention. It is apparent to those skilled in the art that modifications are possible.

According to the present invention as described above, in the automatic exposure control apparatus of the image sensor applied to the camera module, by controlling the appropriate exposure using the average brightness, without using a microcontroller, by changing the shutter speed using a digital filter In addition, it operates actively and at high speed in response to sudden brightness change or frequent brightness change of the image.

In addition, since the average luminance value is converted into an index value and calculated, a high-speed operation is performed so that a signal can be processed in real time, thereby actively operating on a change in luminance of an image.

In addition, the time taken to find the appropriate exposure is not only shortened, but also it can actively cope with the sudden change or frequent brightness changes, and it does not use a microcontroller, so it is an image sensor module made of application specific integrated circuit (ASIC). Can significantly reduce the size.

Claims (12)

And a lens unit for receiving an image, a shutter, and an image sensor unit for capturing an image from the lens unit through the shutter and converting the image into an electrical image signal, and reconstructing the image signal through the image sensor unit as an image. An automatic exposure control apparatus applied to an image sensor module including an image signal processor, A luminance calculator for extracting an average luminance from the image signal from the image signal processor; A luminance correction determining unit determining a speed fixing or a speed correction of the exposure adjustment shutter based on a luminance error value corresponding to an error between the average luminance from the luminance calculating unit and a preset reference luminance; In determining the speed correction, if the luminance error value is within a predetermined microerror range, direct compensation of the speed of the shutter is controlled. If the luminance error value is out of a predetermined microerror range, filtering correction of the speed of the shutter is performed. A correction path control unit controlling the control; A digital filter for filtering the luminance error value and outputting a luminance error filtering value according to the control of the correction path controller; A shutter speed correction unit correcting a current shutter speed value using a luminance error value from the speed correction controller or a luminance error filtering value from the digital filter unit to provide a controlled shutter speed value; And Shutter speed controller for controlling the speed of the shutter included in the image sensor unit by using the control shutter speed value Automatic exposure control device of the image sensor module comprising a. The method of claim 1, wherein the luminance calculator, The automatic exposure control device of the image sensor module, characterized in that for calculating the average luminance of the image at the current shutter speed for each frame. The method of claim 2, wherein the luminance correction determiner, The average brightness index value is converted into an average brightness index value by referring to a first lookup table to which an average brightness index value for each average brightness is mapped in advance, and the reference brightness index and the average brightness index value previously allocated to a preset reference brightness. If the luminance error index value is '0', the current shutter speed value is determined as the control shutter speed value. If the luminance error index value is not '0', the current shutter speed value is determined. Automatic exposure control device of the image sensor module, characterized in that for controlling the correction of. The method of claim 3, wherein the correction path control unit, According to the control of the luminance correction determiner, if the luminance error index value is included in a preset small error range, direct compensation of the current shutter speed index value corresponding to the average luminance is controlled, and is not included in the preset small error range. If not, the automatic exposure control device of the image sensor module, characterized in that for controlling the filtering correction of the current shutter speed index value. The method of claim 4, wherein the digital filter unit, And an luminance error filtering value by filtering the luminance error index value according to the control of the speed compensation controller. The method of claim 5, wherein the shutter speed correction unit, Obtaining a controlled shutter speed index value by correcting the current shutter speed index value using the luminance error index value from the speed correction control part or the luminance error filtering value from the digital filter part. Exposure control device. The method of claim 6, wherein the shutter speed control unit, The control shutter speed index value is converted into a control shutter speed value by referring to a second lookup table to which the control shutter speed value for each control shutter speed index value is mapped in advance. Shutter speed control unit to control the speed Automatic exposure control device of the image sensor module comprising a. The method of claim 4, wherein the predetermined microerror range is, And greater than or equal to '-2' and less than or equal to '2'. The method of claim 5, wherein the digital filter, A multiplier for multiplying a predetermined coefficient by the luminance error index value; An integer converter configured to convert an output value from the multiplier to a nearest integer value and output an error filtering value; A first register for storing a first difference value corresponding to a difference between a luminance error index value and the error filtering value for one previous frame of the current frame of the image signal; A second register for storing a first difference value corresponding to a difference between a luminance error index value and the error filtering value for two previous frames of the current frame of the image signal; And A coefficient selector for selecting one of preset filter coefficients according to the luminance error index value, the first difference value, and the second difference value Automatic exposure control device of the image sensor module comprising a. And a lens unit for receiving an image, a shutter, and an image sensor unit for capturing an image from the lens unit through the shutter and converting the image into an electrical image signal, and reconstructing the image signal through the image sensor unit as an image. An automatic exposure control apparatus applied to an image sensor module including an image signal processor, Calculating an average luminance of the image at the current shutter speed for each frame; An index conversion step of converting the average luminance into an average luminance index value by referring to a first lookup table to which an average luminance index value for each average luminance is mapped in advance; An error calculating step of obtaining a luminance error index value corresponding to an error between a reference luminance index value previously assigned to a preset reference luminance and the average luminance index value; A speed fixing step of determining a current shutter speed value as a control shutter speed value when the luminance error index value is '0'; When the luminance error index value is not '0', when the luminance error index value is included in a preset small error range, the current shutter speed index value is corrected using the luminance error index value to control the shutter speed index value. A direct correction step of determining; A filtering step of obtaining a luminance error filtering value by filtering the luminance error index value when the luminance error index value is not included in a predetermined small error range; A filtering correction step of determining a control shutter speed index value by correcting a current shutter speed index value by using the luminance error filtering value from the digital filter unit; A speed conversion step of converting the control shutter speed index value into a control shutter speed value by referring to a second lookup table to which the shutter speed value for each control shutter speed index value is mapped; And A control step of controlling the speed of the shutter of the image sensor unit using the control shutter speed value Automatic exposure control method of the image sensor comprising a. The method of claim 10, wherein the predetermined microerror range is, And greater than or equal to '-2' and less than or equal to '2'. The method of claim 11, wherein the filter step, A first storing step of storing a first difference value corresponding to a difference between a luminance error index value and the error filtering value for one previous frame of the current frame of the image signal; A second storing step of storing a first difference value corresponding to a difference between a luminance error index value and the error filtering value for two previous frames of the current frame of the image signal; A coefficient selection step of selecting a coefficient among preset filter coefficients according to the luminance error index value, the first difference value, and the second difference value and providing the coefficient to the multiplication step; A multiplication step of multiplying the coefficient by the luminance error index value and outputting a multiplication value; And An integer conversion step of outputting an error filtering value by converting the multiplication value to the nearest integer value Automatic exposure control device of the image sensor module comprising a.

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